Resonator-driven timepiece

ABSTRACT

A resonator-driven timepiece is disclosed comprising a high Q electromechanical resonator which is capable of high excursions without Q degradation. Because of the high excursions, the gear driven by the resonator includes large teeth. The gear is preferably annular with the resonator disposed within the internal dimension of the gear. The resonator is preferably piezoelectrically driven.

United States Patent Inventor Appl. No.

Filed Patented Assignee Hugh M. Baker, Jr. Washington, D.C.

Aug. 29, 1969 July 27, 1971 118 Engineering Corporation Silver Spring, Md.

RESONATOR-DRIVEN TLMEPIECE 6 Claims, 7 Drawing Figs.

US. Cl

mi. CI 0 Field of Search [56] References Cited UNITED STATES PATENTS 3,277,394 10/1966 Holt et al. Primary Examiner-Richard B. Wilkinson Assistant Examiner-Edith C. Simmons Attorney-G. Turner Moller ABSTRACT: A resonator-driven timepiece is disclosed comprising a high Q electromechanical resonator which is capable of high excursions without 0 degradation. Because of the high excursions, the gear driven by the resonator includes large teeth. The gear is preferably annular with the resonator disposed within the internal dimension of the gear. The resonator is preferably piezoelectrically driven.

PATENT ED JUL27 I97:

SHEET 1 0F 2 INVENTOR. HUGH M. BAKER, JR.

FIG. I

ATTORNEYS.

PATENTEDJULNIQH 3595,00?

SHEET 2 BF 2 INVEH'IUR HUGH M4 BAKER, JR

RESONATOR-DRIVEN TIMEPIECE CROSS REFERENCE TO RELATED APPLICATIONS BACKGROUND OF THE INVENTION N Resonator-driven watches are well known in the art and generally comprise a tuning fork, an index finger mounter intermediate the ends of one of the tuning fork tines, a small rachet wheel positioned adjacent the index finger and driven thereby, a more or less conventional gear reduction unit driven by the rachet wheel for moving the second, minute and hour hands of the timepiece, and electromagnetic means for energizing the tuning fork at a predetermined frequency. Watches of this type are found in U.S. Pats. Nos. 2,929,196; 2,949,727; 2,960,817; 2,971,323; 3,057,147 and others. Although a tuning fork has proved to be a successful driving. mechanism for a watch, there are three basic disadvantages of a tuning fork which complicate the construction of a satisfactory and inexpensive resonator-driven watch. First, a tuning fork is susceptible to shock, vibration and orientation which are critical in a watch. Second, the excursion or movement of the tines of a tuning fork is quite small. Third, the Q of a tuning fork is relatively low. In a mechanical resonator, Q is an expression of the amount of energy conserved compared with the amount of energy dissipated.

A consideration of these disadvantages has necessitated the use in a watch of a relatively high frequency tuning fork driving a very small rachet wheel from a position intermediate the ends of the tuning fork tine. As explained in the file wrapper of U.S. Pat. No. 2,971,323, the selection of a relatively high operating resonant frequency is necessary to avoid shock induced variations in the resonant frequency. As pointed out in U.S. Pat. Nos. 3,310,756 and 3,310,757, resilient mounting plates are used for tuning fork driven timepieces in order to minimize the effect of vibration and shock imparted to the base.

The small excursion of the tuning fork tine has necessitated the use of rachet wheel having very small teeth thereon. For example, U.S. Reissue Pat. No. 26,322 states that one operable rachet wheel is 0.095 inch in diameter, containing 300 teeth of 0.008 inch in length. It is a tribute to the patience and persistence of timepiece manufacturers that tuning fork driven watches are presently on the market. The necessity for small rachet wheels having extremely small teeth is aggravated by the necessity of placing the driving index finger intermediate the ends of the tine rather than on the end thereof.

Appropriate placement of the driving index finger of prior prior art tuning fork driven time piece motors is necessary either to limit the energy given up by the tuning fork, to match the mechanical impedance of the tuning fork with the mechanical impedance of the reduction gears or a combination of both. A practicable compromise has been to position the driving index finger intermediate the ends of the tuning fork tine.

It is known in a clock to drive magnetically off of the end of the tuning fork tine. While this is feasible in a clock where the tuning fork is of substantial size, it is not feasible in a watch where the size of the tuning fork is necessarily limited.

generally H-shaped device disclosed in application Ser. No. 565,430. This resonator is not adapted to drive a timepiece mechanism since the excursion of the rigid parts is extremely small. In order to obtain excursions large enough with the H- shaped resonator to drive a rachet WheeL the web must be bowed to such an extent that the Q of the resonator falls off to such an extent that this resonator cannot be used for timepiece motors.

It has been suggested in Japanese Pat. No. 18352, issued Aug. 3, 1968, to use a resonator of the same generic family as here disclosed for a timepiece drive. There is no disclosure in this patent concerning the drive connection from the resonator to the watch reduction gears or the manner in which the resonator is excited.

SUMMARY OF THE INVENTION A timepiece motor is provided comprising a generally annular gear having teeth thereon, a resonator disposed at least partially within the internal dimension of the gear and means carried by the resonator operably driving the gear in accordance with the frequency of the resonator. A timepiece motor is provided comprising a resonator comprised of oppositely rotating rigid parts interconnected by a flexible part inducing counter-rotary movement and producing substantial excursions of the ends of the rigid parts, a gear having teeth thereon and means operatively carried by at least one of the rigid parts adjacent the end thereof for driving the gear in accordance with the frequency of the resonator.

It is an object of the invention to provide a timepiece motor comprised of a resonator which is insensitive to shock and vibration, frequency independent of orientation, having high Q, and which has substantial excursions at the resonator end.

It is another object of the invention to provide a timepiece comprised of a resonator and a gear both of which are generally the same size as the internal chamber of the timepiece.

A further object of the invention is to provide a timepiece motor comprised of an annular gear and a resonator operatively driving the gear and disposed at least partially within the internal dimension thereof.

A still further object of the invention is to provide a timepiece motor comprised of a resonator operatively driving a gear or rachet wheel from adjacent the end of the resonator.

Further objects, advantages and important features of this invention will be apparent from a study of the specification following taken with the drawing which together describe and disclose preferred embodiments of the invention and what is now considered and believed to be the best mode of practicing the principles thereof. Still other embodiments, modifications or equivalents may be apparent to those having the teachings herein.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a timepiece motor in accordance with the principles of the invention;

FIG. 2 is a cross-sectional view of the timepiece motor of FIG. 1, taken substantially along line 2-2 thereof as viewed in the direction of the arrows;

FIG. 3 is a partial view of a portion of the timepiece motor of FIG. 1 illustrating the cooperation between a resonator and a rachet wheel at one-half cycle of resonator operation;

FIG. 4 is another partial view of the timepiece motor of FIG. 1 illustrating the cooperation between the resonator and rachet wheel at another half-cycle of resonator operation;

FIG. 5 is a plan view of another resonator which may be used in a time piece in accordance with the principles of the invention;

FIG. 6 is an end view of the resonator of FIG. 5; and

FIG. 7 is an enlarged cross-sectional view of one embodiment of a timepiece made in accordance with the principles of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS Attention is directed to FIGS. 1 and 2 wherein there is shown a timepiece motor comprised of a resonator 12, an annular gear 14 and means 16 driving the gear 14 in accordance with the frequency of the resonator 12.

The resonator 12 comprises a pair of parts 18, 20 which are pivotally mounted by supporting pins 22, 24 extending from a base 26 for enabling the parts 18, 20 to rotate about the respective nodal axes 28, 30 thereof. The supporting pins 22, 24 may be of any convenient type but are illustrated as comprising a pin 32, 34 affixed to the base 26 and surrounded by a resilient collar 36, 38 positioned in a similarly configured aperture in the rigid parts 18, 20.

The parts 18, 20 are configured such that the mass moments of inertia are generally equal and such that the centers of gravity 40, 42 are substantially intersected by the nodal axes 28, 30. The parts 18, 20 are called rigid or bodily rigid which meansthat they are unflexing at a resonant frequency of the resonator 10 although they may be flexible at higher frequencies. The rigid parts 18, 20 are provided with aligned large cutouts 44, 46 and somewhat smaller aligned cutouts 48, 50 which together provide for the connection of a third part 52 to the first and second parts 18, 20 and also accommodate movement of the third part 52. The third part 52 is connected to the rigid parts 18, 20 in the small cutouts 48, 50 in any suitable manner.

The third part 52 is termed flexible or bodily flexible which means that it flexes at a resonant frequency of the resonator 10 although it may be inflexible at lower frequencies. The third part 52 is preferably flexed by a piezoelectric wafer 54 afi'ixed to the web 52 and controlled by electrical energy delivered through a pair of wires 56. Application of voltage of one polarity through the wires 56 expands the piezoelectric wager 54 affixed to the web 52 and controlled by electrical energy delivered through a pair of wires 56. Application of voltage of one polarity rough a pair of wires 56 expands the piezoelectric wafer 54 thereby bending the web or third part 52 into an upwardly convex configuration illustrated in long dash lines in FIG. 1. Because of the connection between the web 52 and the rigid parts 18, 20, the parts 18, 20 are counterrotated into the position illustrated by the long dash lines in FIG. 1. In a similar manner, application of voltage of opposite polarity through the wires 54 contracts the piezoelectric wafer 54 thereby bending the web 52 into the upwardly concave position shown in short dash lines. Accordingly, the rigid parts 18, 20 are counterrotated to assume a position indicated by the short dash lines in FIG. 1. It will be appreciated that the dash lines illustrated in FIG. 1 are somewhat exaggerated. A more complete description of the operation of this type of resonator is shown in the publication above cited.

The only substantial difference between the resonators here disclosed and the resonators in these publications is the point of connection between the web and the rigid parts. As shown in FIG. 1 of the Radio Club of America publication, the flexible web is secured to the inner edges of the rigid members which presents a web of short extent with the resonator consequently having a movement or excursions of the rigid parts which is too small to drive a rachet wheel of a watch. The flexible art 52 may be described from time to time as being connected to the first and second parts to produce substantial excursions at the ends of the rigid parts. This'terminology is intended to exclude resonators of the type disclosed in the cited publications.

As will be pointed hereinafter with respect to FIG. 7 and 8, the provision of the piezoelectric wafer 54 provides a substantial advantage in timepiece motors and particularly in watch motors. It will be apparent that the piezoelectric wafer 54 does not require any additional space in a timepiece case but instead utilized previously unused space within the external confines of the resonator. This is obviously contrasted with the electromagnetic coils used in the previously cited patents which require additional case space. Although tuning forks may theoretically be driven by a piezoelectric wafer, a piezoelectrically driven tuning fork has such a low O that it is impracticable to take additional energy from the tuning fork for driving a rachet wheel. For example, a very good undriven wrist watch size tuning fork has a Q of about 1,000. Driving a tuning fork electromechanically does not catastrophically degrade the Q of the resonator. An electromagnetically driven wrist watch size tuning fork which has an unloaded Q of about 1,000 has a Q of about 350 when used to drive a rachet wheel. An unloaded tuning fork of this size and quality which is driven by a piezoelectric wafer has a Q of about less than which leaves little energy remaining to drive the rachet wheel.

On the other hand, a piczoclectrically driven resonator of the type shown in the cited publications has a Q of about 1,000. Although Q has not been measured with the type of resonator disclosed herein, calculations indicate that 0 would not be substantially different than the already commercial H- shaped resonator in the publications. Consequently, a piezoelectric wafer can be used in these types of resonators and still provide high Q.

The annular gear 14 is illustrated as having internal teeth 58 with the resonator 12 residing within the internal dimension of the annulus. It will be apparent this is of considerable importance in a watch where space is at a premium. The driving means 16 comprises a pair of pawls or index fingers 60, 62 which comprise a resilient strip 64, 66 secured at one end to the rigid parts 18, 20 adjacent the end thereof. A tip 68, 70 is provided on the ends of the resilient strips 64, 66 for engaging the teeth 58 on the gear 14. Similar pawls 72, 74 may be provided adjacent the opposite ends of the rigid parts 18, 20 in order to balance the extraction of energy from the rigid parts 18, 20.

As the rigid parts 18, 20 counter rotate into the position shown by the short dashed lines in FIG. 1, the parts will assume the operative relationship shown in FIG. 3. It will be apparent that as the pawl 60 rotates the gear 14 in the direction shown by the arrow, the pawl 62 is cammed out of engagement with five and into driving engagement with the tooth numbered four. As the rigid parts 18, 20 are driven into the position shown by the long dashed lines in FIG. 1 the pawl 62 drives the gear 14 in the direction shown by the arrow in FIG. 4 while the pawl 60 is cammed downwardly by the tooth numbered two preparatory to the reversal of movement. It will be noted that the amplitude of oscillation of the rigid parts 18, 20 is greater than the adjacent teeth 58 and less than the spacing between two adjacent teeth 58 on the gear 14. The amplitude of movement of the rigid parts 18, 20 may be controlled as shown in US. Pats. Nos. 2,929,196; 2,971,323; 2,960,817 or in any other suitable manner.

Referring now to FIGS. 5 and 6, there is disclosed another resonator 112 which is suitable for timepiece motor use. For purposes of brevity, analogous reference characters are used to indicate analogous elements, most of which will not be specifically discussed. The major difference between the embodiment of FIGS. 5 and 6 and the embodiment of FIGS. 1 and 2 resides in the locations where the web 152 is connected to the rigid parts 118, 120. The web 152 is connected to one end of the rigid part 118 through a bent end 172 while the other end of the third part 152 is connected to the opposite end of the rigid part by a bent end 174. The resonator 112 is substantially identical to the resonators shown in FIG. 12 in application Ser. No. 714,221 and has all of the necessary characteristics for timepiece motor use as do all of the remaining resonators of this application.

The operation of the resonator 112 is substantially the same as the operation of the resonator 12. Application of a voltage of predetermined polarity through the wires 156 expands the piezoelectric means 154 to bow the web 152 into a leftward concave configuration counter rotating the rigid parts 118, 120 to separate the pawls 160, 162. The pawl 160 operates to drive the gear (not shown) while the pawl 162 is cammed by one of the gear teeth into a position to drive the gear upon the reversal of movement of the parts 118, 120. Application ofa voltage of opposite polarity. through the wires 156 operates to contract the piezoelectric means 154 which bows the web 152 into a rightward concave relationship to counter-rotate the parts 118, 120. The pawls 160, 162 approach each other with the pawl 160 driving the gear (not shown) while the pawl 160 is cammed into a position to drive the gear upon reversal of movement of the parts 118, 120.

Referring now to FIG. 7, there is illustrated a watch 200 having as an integral part thereof the timepiece motor 10. The resonator base 26 is used as the support for the remaining elements of the watch 200. The watch 200 comprises a transparent front wall 202 and a backwall 204. A timepiece dial plate 206 is arranged behind the front wall 202 and attached to the base 26 by a suitable spacer 208. The annular gear 14 is connected to a shaft 210 by a spoke arrangement 212. The shaft 210 is disposed between the rigid parts 18, and spaced from the web 52. The shaft 210 is journaled in a passage 214 in the base 26. A conventional watch gear reduction unit 216 operatively connects the shaft 210 to a second hand shaft 218, a minute shaft 220 and an hour hand shaft 222 in a suitable manner.

A battery 224 is removably mounted on the base 26 and is electrically connected to suitable circuitry (not shown) for alternately applying of voltages of opposite polarity to the piezoelectric means 54. The electrical circuitry may, for example, be disposed on the base 26. The rigid part 18 is illustrated as cut away at 226 to provide adequate clearance adjacent the battery 224. A similar cutout 228 is provided on the opposite end of the rigid member 18 to ensure that the center of gravity of the member 18 does not move from adjacent the nodal axis. It will be apparent that the cutouts 226, 228 need be provided only adjacent the ends of the rigid member 18.

Although the organization of the components of the watch 200 is the best mode of practicing the principles of the invention, it will be apparent that other placements of the component pans are practicable. It will be seen that the provision of a piezoelectric wafer 54 disposed substantially within the internal confines of the resonator l2 conserves considerable space in the case provided by the front and rear walls 202, 204. By the term external dimensions of the resonator, it is intended to mean the dimensions required by the resonator to oscillate freely rather than the external dimensions of the resonator at rest.

It will be seen that providing the resonator 12 at least partially within the internal dimension of the gear 14 likewise conserves space within the timepiece case and allows for a watch of minimum thickness. Since the resonators 12, 112 are of a type having substantial excursions at the end of the rigid parts without degrading the Q of the resonator, the gear 14 may be driven off of the ends of the rigid parts thereby enabling the use of a gear having substantial sized teeth as compared to prior art resonator driven rachet wheels.

lclaim:

1. A timepiece motor comprising a generally annular gear having teeth thereon; a resonator disposed at least partially within the internal dimension of the gear; and

means carried by the resonator operatively driving the gear in accordance with the frequency of the resonator.

2. The timepiece motor of claim 1 wherein the resonator defines a plane generally parallel to the annular gear.

3. The timepiece motor of claim 1 wherein the resonator comprises a plane coincident with the plane of the annular gear.

4. The timepiece motor of claim 1 wherein the gear teeth are on the internal diameter thereof.

5. The timepiece motor of claim 1 wherein the teeth define ratchet teeth and the driving means comprises an index finger.

6. The timepiece motor of claim 5 wherein the resonator comprises oppositely moving parts, the index finger is affixed to one of the moving parts and the driving means further comprises another index finger secured to the other part the gear emg successively rotated by one and then by the other index finger, the driving movement of one of the index fingers corresponding to the return movement of the other. 

1. A timepiece motor comprising a generally annular gear having teeth thereon; a resonator disposed at least partially within the internal dimension of the gear; and means carried by the resonator operatively driving the gear in accordance with the frequency of the resonator.
 2. The timepiece motor of claim 1 wherein the resonator defines a plane generally parallel to the annular gear.
 3. The timepiece motor of claim 1 wherein the resonator comprises a plane coincident with the plane of the annular gear.
 4. The timepiece motor of claim 1 wherein the gear teeth are on the internal diameter thereof.
 5. The timepiece motor of claim 1 wherein the teeth define ratchet teeth and the driving means comprises an index finger.
 6. The timepiece motor of claim 5 wherein the resonator comprises oppositely moving parts, the index finger is affixed to one of the moving parts and the driving means further comprises another index finger secured to the other part, the gear being successively rotated by one and then by the other index finger, the driving movement of one of the index fingers corresponding to the return movement of the other. 